In a known fastener of this kind, described in our British Pat. No. 1538423, the engaging means of the bolt comprises a plurality of annular barbs in a suitable position on the shank of the bolt and the engaging means of the body comprises a resiliently deformable part into which the barbs of the bolt are able to embed so as to resist withdrawal of the bolt from the body once they are interengaged.
The bolt has a tail portion which can pass freely through the body, whereby the bolt can be gripped and pulled relative to the body by a suitable tool so as to clamp together the members to be fastened and cause interengagement of the engaging means, and which portion breaks off from the rest of the bolt at a predetermined tensile load, leaving the rest of the bolt together with the interengaged body to fasten the members together.
The known fastener has been used extensively in the construction of freight containers, in which it has been found satisfactory for securing, to a metallic supporting framework, panels of such materials as plywood which may have a face-covering skin of plastics material, particularly glass fiber reinforced plastics material, which is engaged by the flange of the body of the fastener. Such panel materials are sufficiently resistant to withstand the pressure with which the flange is forced to bear against the face of the panel.
However, this is not so in the case of panels known as "sandwich panels" or "honeycomb board", consisting of a cellular matrix secured by adhesion between two sheets of reinforced plastics material, which are less resistant to localized compressive loads and which also tend to show variations in thickness due to tolerances in manufacture. Such panels can suffer damage in or around the zone on which the flange bears, due to the compression load applied during setting of the fastener before reaching the predetermined load at which the bolt will break.